Single diffusion break isolation for gate-all-around field-effect transistor devices

ABSTRACT

Devices and methods are provided for forming single diffusion break isolation structures for integrated circuit devices including gate-all-around FET devices such as nanosheet FET devices and nanowire FET devices. For example, a semiconductor integrated circuit device includes first and second gate-all-around field-effect transistor devices disposed in first and second device regions, respectively, of a semiconductor substrate. A single diffusion break isolation structure is disposed between the first and second device regions. The single diffusion break isolation structure includes a dummy gate structure disposed on the semiconductor substrate between a first source/drain layer of the first gate-all-around field-effect transistor device and a second source/drain layer of the second gate all-around field-effect transistor device. The single diffusion break isolation structure is configured to electrically isolate the first and second source/drain layers.

TECHNICAL FIELD

This disclosure relates generally to semiconductor fabricationtechniques and, in particular, to techniques for isolatinggate-all-around (GAA) field-effect transistor (FET) devices such asnanosheet FET devices.

BACKGROUND

Continued innovations in semiconductor process technologies are enablinghigher integration densities and device scaling. As the semiconductorindustry moves towards the 7-nm technology node and beyond,semiconductor FET device structures must be scaled to smaller dimensionsto provide increased device width per footprint area. In this regard,non-planar FET devices such as nanosheet FET devices, nanowire FETdevices, vertical FET devices, FinFET devices, etc., are a viable optionfor continued CMOS scaling. In general, a nanowire FET device comprisesa device channel which comprises one or more nanowire layers in astacked configuration, wherein each nanowire comprises an elongatedsemiconductor channel layer that has a width which is substantially thesame as a thickness of the elongated semiconductor channel layer. Ananosheet FET device is similar to a nanowire FET device sheet in that adevice channel comprises one or more nanosheet channel layers in astacked configuration, but wherein each nanosheet channel layer has awidth which is substantially greater than a thickness of the nanosheetchannel layer. In GAA FET devices such as nanowire/nanosheet FETdevices, the gate material is formed to surround all sides of the activechannel layers of such FET devices. In addition, with nanowire/nanosheetFET devices, a common gate structure is formed above and below eachnanowire/nanosheet layer in the stacked configuration, therebyincreasing the FET device width (or channel width), and thus the drivecurrent, for a given footprint area.

The FET devices formed in different active areas of a semiconductorintegrated circuit device must be electrically isolated from one anotherto properly form an integrated circuit. Various techniques are usedisolate active device areas comprising cells/arrays of FET devices. Forexample, shallow trench isolation methods can be used to form shallowtrench isolation regions between active device regions. However, theformation of shallow isolation regions and structures can consume asignificant amount of valuable footprint area on the substrate. Thisbecomes increasing problematic with smaller scaling and increasingdevice packing densities, wherein it can be difficult to form suchisolation structures. Within the semiconductor fabrication industry,other types of isolation structures/regions that may be formed arereferred to as “diffusion breaks.” Such diffusion breaks are formed withisolation material disposed between active device regions. A doublediffusion break (DDB) refers to an isolation structure having a lateralwidth (in a current transport direction or gate length direction of FETdevices) between two active regions which approximately corresponds tothe lateral width of two gate structures of the FET devices. A singlediffusion break (SDB) refers to an isolation structure having a lateralwidth (in the current transport direction or gate length direction ofthe FET devices) between two active regions is less than the lateralwidth of a single gate structure of the FET devices. The use of DDBisolation structures consumes significantly more footprint space on asubstrate as compared to SDB isolation structures, thereby leading toreduced packing densities.

SUMMARY

Embodiments of the invention include methods for forming singlediffusion break isolation structures for integrated circuit devicescomprising gate-all-around FET devices such as nanosheet FET devices andnanowire FET devices.

For example, an exemplary embodiment includes a semiconductor integratedcircuit device which comprises a first gate-all-around field-effecttransistor device disposed in a first device region of a semiconductorsubstrate, a second gate-all-around field-effect transistor devicedisposed in a second device region of the semiconductor substrate, and asingle diffusion break isolation structure disposed between the firstand second device regions. The single diffusion break isolationstructure comprises a dummy gate structure disposed on the semiconductorsubstrate between a first source/drain layer of the firstgate-all-around field-effect transistor device and a second source/drainlayer of the second gate all-around field-effect transistor device,wherein the single diffusion break isolation structure is configured toelectrically isolate the first and second source/drain layers.

Another embodiment includes a method for fabricating a semiconductorintegrated circuit device, which comprises forming a firstgate-all-around field-effect transistor device in a first device regionof a semiconductor substrate, forming a second gate-all-aroundfield-effect transistor device in a second device region of thesemiconductor substrate, and forming a single diffusion break isolationstructure between the first and second device regions. The singlediffusion break isolation structure comprises a dummy gate structureformed on the semiconductor substrate between a first source/drain layerof the first gate-all-around field-effect transistor device and a secondsource/drain layer of the second gate all-around field-effect transistordevice, wherein the single diffusion break isolation structure isconfigured to electrically isolate the first and second source/drainlayers.

Other embodiments will be described in the following detaileddescription of embodiments, which is to be read in conjunction with theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 7 schematically illustrate a method for fabricating asemiconductor integrated circuit (IC) device having single diffusionbreak isolation structures for isolating nanosheet FET devices,according to an exemplary embodiment of the invention, wherein:

FIG. 1A is a schematic top plan view of the semiconductor IC device atan initial stage of fabrication comprising a plurality of nanosheet FETdevices formed on a semiconductor substrate;

FIG. 1B is a schematic cross-sectional side view of the semiconductor ICdevice along line 1B-1B in FIG. 1A;

FIG. 2 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIGS. 1A and 1B after forming an etch maskwhich comprises an opening to expose a gate structure in a singlediffusion break region and after removing dummy gate layers of theexposed gate structure to expose nanosheet stack structures in thesingle diffusion break region;

FIG. 3 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 2 after performing an anisotropic etchprocess to vertically etch the exposed nanosheet stack structures in thesingle diffusion break region down to a surface of the semiconductorsubstrate;

FIG. 4 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 3 after removing the etch mask andperforming an oxidation process to oxidize remaining end portions ofnanosheet channel layers of the etched nanosheet stack structures andthereby form oxide layers;

FIG. 5 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 4 after filling open gate region withinsulating material to thereby complete formation of a single diffusionbreak isolation structure between active device regions;

FIG. 6 is a schematic cross-sectional view of the intermediate devicestructure shown in FIG. 5 after removing dummy gate capping layers andthe dummy gate sacrificial layers of gate structures in active deviceregions, and after removing sacrificial nanosheet layers to releaseactive nanosheet channel layers of the nanosheet stack structures of thenanosheet FET devices and form open gate regions; and

FIG. 7 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 6 after forming high-k dielectric/metalgate structures for the gate structures of the nanosheet FET devices.

FIGS. 8 through 10 schematically illustrate a method for fabricating asemiconductor IC device having single diffusion break isolationstructures for isolating nanosheet FET devices, according to anotherexemplary embodiment of the invention, wherein:

FIG. 8 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 3 after removing the etch mask and afterremoving remaining end portions of nanosheet channel layers of theetched nanosheet stack structures in the single diffusion break regionto thereby form recess regions between first embedded sidewall spacers;

FIG. 9 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 8 after filling the recess regions withdielectric material to form second embedded sidewall spacers between thefirst embedded sidewall spacers; and

FIG. 10 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 9 after filling the open gate region withinsulating material to thereby complete formation of a single diffusionbreak isolation structure between active device regions.

FIGS. 11 and 12 schematically illustrate a method for fabricating asemiconductor IC device having single diffusion break isolationstructures for isolating nanosheet FET devices, according to anotherexemplary embodiment of the invention, wherein:

FIG. 11 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 2 after removing the etch mask and afterselectively etching away sacrificial nanosheet layers of the exposednanosheet stack structures in the single diffusion break region; and

FIG. 12 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 11 after oxidizing the exposed nanosheetchannel layers in the single diffusion break region to form oxidelayers, and after filling the open gate region with insulating materialto thereby complete formation of a single diffusion break isolationstructure between active device regions.

FIGS. 13A through 16 schematically illustrate a method for fabricating asemiconductor IC device having single diffusion break isolationstructures for isolating nanowire FET devices, according to an exemplaryembodiment of the invention, wherein:

FIG. 13A is a schematic top plan view of the semiconductor IC device atan initial stage of fabrication comprising a plurality of nanowire FETdevices formed on a semiconductor substrate;

FIG. 13B is a schematic cross-sectional side view of the semiconductorIC device along line 13B-13B in FIG. 13A;

FIG. 14 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIGS. 13A and 13B after removing dummy gatelayers of a gate structure in a single diffusion break region to form anopen gate region which exposes nanowire stack structures in the singlediffusion break region, and after selectively etching away nanowirechannel layers of the exposed nanowire stack structures in the singlediffusion break region to form spaces between sacrificial nanowirelayers of the exposed nanowire stack structures;

FIG. 15 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 14 after forming dielectric layers in thespaces between the sacrificial nanowire layers; and

FIG. 16 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIG. 15 after filling the open gate regionwith insulating material to thereby complete formation of a singlediffusion break isolation structure between active device regions.

DETAILED DESCRIPTION

Embodiments of the invention will now be described in further detailwith regard to methods for fabricating semiconductor integrated circuitdevices having single diffusion break isolation structures for isolatinggate-all-around FET devices such as nanosheet FET devices and nanowireFET devices. It is to be understood that the various layers, structures,and regions shown in the accompanying drawings are schematicillustrations that are not drawn to scale. In addition, for ease ofexplanation, one or more layers, structures, and regions of a typecommonly used to form semiconductor devices or structures may not beexplicitly shown in a given drawing. This does not imply that anylayers, structures, and regions not explicitly shown are omitted fromthe actual semiconductor structures. Furthermore, it is to be understoodthat the embodiments discussed herein are not limited to the particularmaterials, features, and processing steps shown and described herein. Inparticular, with respect to semiconductor processing steps, it is to beemphasized that the descriptions provided herein are not intended toencompass all of the processing steps that may be required to form afunctional semiconductor integrated circuit device. Rather, certainprocessing steps that are commonly used in forming semiconductordevices, such as, for example, wet cleaning and annealing steps, arepurposefully not described herein for economy of description.

Moreover, the same or similar reference numbers are used throughout thedrawings to denote the same or similar features, elements, orstructures, and thus, a detailed explanation of the same or similarfeatures, elements, or structures will not be repeated for each of thedrawings. It is to be understood that the terms “about” or“substantially” as used herein with regard to thicknesses, widths,percentages, ranges, etc., are meant to denote being close orapproximate to, but not exactly. For example, the term “about” or“substantially” as used herein implies that a small margin of error ispresent, such as 1% or less than the stated amount.

The term “exemplary” as used herein means “serving as an example,instance, or illustration”. Any embodiment or design described herein as“exemplary” is not to be construed as preferred or advantageous overother embodiments or designs. The word “over” as used herein to describeforming a feature (e.g., a layer) “over” a side or surface, means thatthe feature (e.g. the layer) may be formed “directly on” (i.e., indirect contact with) the implied side or surface, or that the feature(e.g., the layer) may be formed “indirectly on” the implied side orsurface with one or more additional layers disposed between the feature(e.g., the layer) and the implied side or surface.

To provide spatial context to the different structural orientations ofthe semiconductor structures shown throughout the drawings, XYZCartesian coordinates are shown in each of the drawings. The terms“vertical” or “vertical direction” or “vertical height” as used hereindenote a Z-direction of the Cartesian coordinates shown in the drawings,and the terms “horizontal,” or “horizontal direction,” or “lateraldirection” as used herein denote an X-direction and/or a Y-direction ofthe Cartesian coordinates shown in the drawings.

FIGS. 1A through 7 schematically illustrate a method for fabricating asemiconductor integrated circuit (IC) device having single diffusionbreak isolation structures for isolating nanosheet FET devices,according to an exemplary embodiment of the invention. To begin, FIGS.1A and 1B schematically illustrate a semiconductor IC device 10 at aninitial stage of fabrication comprising a plurality of nanosheet FETdevices D1, D2, D3, and D4 formed on a semiconductor substrate 100. FIG.1A is a schematic top plan view (X-Y plane) of the semiconductor ICdevice 10 and FIG. 1B is a schematic cross-sectional side view (X-Zplane) of the semiconductor IC device 10 along line 1B-1B in FIG. 1A. Asshown in FIGS. 1A and 1B, the semiconductor IC device 10 comprises afirst active region R1 and a second active region R2, which areseparated by a single diffusion break region R3. The nanosheet devicesD1 and D3 are disposed in the first active region R1 and the nanosheetdevices D2 and D4 are disposed in the second active region R2.

The nanosheet device D1 comprises a nanosheet stack structure 110-1 andsource/drain layers 130 and 131. The nanosheet device D2 comprises ananosheet stack structure 110-2 and source/drain layers 132 and 133. Thenanosheet device D3 comprises a nanosheet stack structure 110-3 andsource/drain layers 134 and 135. The nanosheet device D4 comprises ananosheet stack structure 110-4 and source/drain layers 136 and 137. Thesingle diffusion break region R3 comprises a nanosheet stack structure110-5 disposed between the source/drain layers 131 and 132, and ananosheet stack structure 110-6 disposed between the source/drain layers135 and 136. The nanosheet stack structures 110˜1110-6 each comprise aplurality of epitaxial semiconductor layers 111, 112, 113, 114, 115,116, and 117, which include sacrificial nanosheet layers 111, 113, 115,and 117, and active nanosheet channel layers 112, 114, and 116, whereineach active nanosheet channel layer 112, 114, and 116 is disposedbetween sacrificial nanosheet layers. It is to be understood that theterm “source/drain layer” as used herein means that a given source/drainlayer can be either a source or drain of a nanosheet FET device,depending on the application or circuit configuration.

The semiconductor IC device 10 further comprises a plurality of gatestructures G1, G2 and G3. The gate structure G1 is disposed in the firstactive region R1 and overlaps the nanosheet stack structures 110-1 and110-3 of the respective nanosheet FET devices D1 and D3. The gatestructure G2 is disposed in the second active region R2 and overlaps thenanosheet stack structures 110-2 and 110-4 of the respective nanosheetFET devices D2 and D3. The gate structure G3 is disposed in the singlediffusion break region R3 and overlaps the nanosheet stack structures110-5 and 110-6. At the stage of fabrication shown in FIGS. 1A and 1B,the gate structures G1, G2, and G3 comprise dummy gate structures,wherein each gate structure G1, G2 and G3 comprises a dummy gate oxidelayer 120, a dummy gate electrode layer 122 (e.g., sacrificialpolysilicon or amorphous silicon material), a gate capping layer 124, agate sidewall spacer 126, and embedded sidewall spacers 128. The gatestructures G1, G2, and G3 and the source/drain layers 130-133 areencapsulated in a layer of insulating material 140 (e.g., an interleveldielectric (ILD) layer).

As explained in further detail below, the dummy gate oxide layers 120and the dummy gate electrode layers 122 of the gate structures G1 and G2comprise sacrificial gate material which is subsequently removed as partof a replacement metal gate (RMG) process and replaced with a high-kgate dielectric material and metallic material to form a common high-kdielectric/metal gate (HKMG) structure for the nanosheet FET devices D1and D3 in the first active region R1, and a common HKMG structure forthe nanosheet FET devices D2 and D4 in the second device region R2.Furthermore, as explained in further detail below, a single diffusionbreak process is performed to remove the dummy gate oxide layers 120 andthe dummy gate electrode layers 122 of the gate structure G3 as well asremove and/or oxidize or otherwise replace the nanosheet stackstructures 110-5 and 110-6 with insulating material in the diffusionbreak region R3 to thereby isolate the source/drain layers 131 and 132of the adjacent nanosheet devices D1 and D2 in the different activeregions R1 and R2, as well as isolate the source/drain layers 135 and136 of the adjacent nanosheet devices D3 and D4 in the different activeregions R1 and R2.

The intermediate structure of the semiconductor IC device 10 shown inFIGS. 1A and 1B is formed using known fabrication methods. While thesemiconductor substrate 100 is illustrated as a generic substrate layerfor ease of illustration, it is to be understood that the semiconductorsubstrate 100 may comprise one of different types of semiconductorsubstrate structures and materials. For example, in one embodiment, thesemiconductor substrate 100 can be a bulk semiconductor substrate (e.g.,wafer) that is formed of silicon (Si) or germanium (Ge), or other typesof semiconductor substrate materials that are commonly used in bulksemiconductor fabrication processes such as a silicon-germanium alloy,compound semiconductor materials (e.g. III-V), etc. In otherembodiments, the semiconductor substrate 100 may be an SOI(silicon-on-insulator) substrate, a GeOI (germanium-on-insulator)substrate, or other types of semiconductor-on-insulator substrates,which comprise an insulating layer (e.g., oxide layer) disposed betweena base substrate layer (e.g., silicon substrate) and an activesemiconductor layer (e.g., Si, Ge, etc.) on which active circuitcomponents are formed as part of a front-end-of-line (FEOL) structure.It is to be noted that in each drawing, the X-Y plane represents a planethat is parallel to the plane of the semiconductor substrate 100 (e.g.,wafer) being processed.

The nanosheet stack structures 110-1˜110-6 are fabricated by a processwhich comprises sequentially growing a stack of epitaxial semiconductorlayers 111, 112, 113, 114, 115, 116, and 117 over the surface of thesemiconductor substrate 100, and then patterning the stack of epitaxialsemiconductor layers 111, 112, 113, 114, 115, 116, and 117 (or nanosheetlayer stack 111-117) to form the individual nanosheet stack structures110-1˜110-6. In one embodiment, the epitaxial semiconductor layers111-117 comprise single crystal (monocrystalline) semiconductormaterials, which are epitaxially grown using known methods such aschemical vapor deposition (CVD), metal-organic chemical vapor deposition(MOCVD), low pressure chemical vapor deposition (LPCVD), molecular beamepitaxy (MBE), vapor-phase epitaxy (VPE), liquid-phase epitaxy (LPE),metal organic molecular beam epitaxy (MOMBE), rapid thermal chemicalvapor deposition (RTCVD), low-energy plasma deposition (LEPD),ultra-high vacuum chemical vapor deposition (UHVCVD), atmosphericpressure chemical vapor deposition (APCVD), liquid-phase epitaxy (LPE),metal-organic chemical vapor deposition (MOCVD), or other knownepitaxial growth techniques which are suitable for the given processflow. The type of materials that are utilized to form the epitaxialsemiconductor layers 111-117 will depend on the application.

For example, in one embodiment, the active nanosheet channel layers 112,114, and 116 are formed of epitaxial silicon (Si). When the activenanosheet channel layers 112, 114, and 116 are formed of crystalline Si,the sacrificial nanosheet layers 111, 113, 115, and 117 (which serve assacrificial layers that are subsequently etched away to release theactive nanosheet channel layers 112, 114, and 116), can be formed of anepitaxial silicon-germanium (SiGe) alloy. This allows the epitaxial SiGematerial of the sacrificial nanosheet layers 111, 113, 115, and 117 tobe etched selective to the epitaxial Si material of the semiconductorchannel layers 112, 114, and 116 in a subsequent process step to“release” the active nanosheet channel layers 112, 114, and 116. Inother embodiments, the active nanosheet channel layers 112, 114, and 116can be formed of an epitaxial SiGe material with a desired Geconcentration (optimized for device performance), and the sacrificialnanosheet layers 111, 113, 115, and 117 can be formed of a sacrificialsemiconductor material (e.g., Si) that can be etched selective to theactive nanosheet channel layers 112, 114, and 116. While the nanosheetstack structures 110-1˜110-6 are shown to include three active nanosheetchannel layers 112, 114, and 116, in other embodiments, the nanosheetstack structures 110-1˜110-6 can be fabricated with more or less thanthree active nanosheet channel layers.

In one embodiment, the nanosheet stack structures 110-1˜110-6 arepatterned using a first etch process that is performed to define a gatewidth Gw of elongated nanosheet stack structures (intermediate nanosheetstack structures) which traverse the different regions R1, R2 and R3,and a second etch process that is subsequently performed to define anoverall length L of the nanosheet stack structures 110-1˜110-6, asillustrated in FIG. 1A. The first etch process is performed by formingan etch mask (e.g., a lithographic mask) over the initial nanosheetlayer stack 111-117, and then transferring an image of the etch maskinto the nanosheet layer stack 111-117 using dry etch process (e.g.,reactive ion etching (RIE)). The etch mask can be formed using anysuitable patterning process including, but not limited to, aphotolithography process, or a multi-patterning process such as asidewall image transfer (SIT) process, a self-aligned double patterning(SADP) process, a self-aligned quadruple pattering (SAQP), etc. Theetching can be performed using one or more sequential dry etch processeswith etch chemistries that are suitable to etch the materials ofsemiconductor layers 111-117.

Although not shown in the Figures, an isolation layer (e.g., shallowtrench isolation (STI) layer) can be formed following the initial etchprocess that is performed to pattern the nanosheet layer stack 111-117.For example, as part of the initial etch process, the exposed portion ofthe upper surface of the semiconductor substrate 100 can be recessed toa target depth to form trenches in the semiconductor substrate 100 whichsurround the intermediate elongated nanosheet stack structures (withdefined gate widths Gw). The trenches are then filled with an insulatingmaterial to form STI layers. In one embodiment, the STI layers areformed by a process which comprises depositing a layer of insulatingmaterial over the surface of the semiconductor structure to cover thepartially formed nanosheet stack structures, planarizing the surface ofthe semiconductor structure (via chemical mechanical polishing (CMP))down to an upper surface of the partially formed nanosheet stackstructures to remove the overburden insulating material, and thenperforming an etch-back (or recess) process to recess the remaininglayer of insulating material down to a target level which defines athickness of the STI layer. The STI layers can be formed of any type ofinsulating material, such a silicon oxide material, which is suitablefor the given fabrication process flow.

Following the initial etch process to pattern the nanosheet layer stack111-117, the dummy gate structures G1, G2 and G3 are formed. The dummygate structure are formed using known methods. For example, a thinconformal layer of silicon oxide is first deposited over the entiresurface of the semiconductor IC device, followed by a blanket depositionof a layer of polysilicon (or alternatively, amorphous silicon) over theconformal layer of silicon oxide, and planarization of the polysiliconlayer. A hard mask layer is formed on the planarized surface of thepolysilicon layer by depositing a layer of dielectric material ormultiple layers of dielectric materials (e.g., SiN, SiOCN, SiBCN). Thehard mask layer is then patterned to form the gate capping layers 124,which define an image of the gate structures G1, G2 and G3. The gatecapping layers 124 are utilized as an etch hardmask to anisotropicallyetch (e.g., RIE) the sacrificial polysilicon and oxide layers to therebyform the dummy gate layers 120 and 122.

The gate sidewall spacers 126 are then formed by depositing a conformallayer of dielectric material over the entire surface of thesemiconductor IC device 10. The conformal layer of dielectric materialcan be formed of SiN, SiBCN, SiCON, or any other type of low-kdielectric material that is commonly used to form insulating gatesidewall spacers of FET devices, and deposited using known techniquessuch as ALD, CVD and PVD. The conformal layer of dielectric material isthen patterned by performing an anisotropic dry etch process, such asRIE, to etch down the conformal layer of dielectric material in avertical direction. This etch process is performed selective to thesemiconductor materials of the intermediate nanosheet stack structures.The etch process results in the formation of the gate sidewall spacers126, which surrounds the dummy gate layers 120 and 122 and the gatecapping layers 124, as shown in FIGS. 1A and 1B.

After forming the gate sidewall spacers 126, an anisotropic dry etchprocess (e.g., RIE) is performed to etch the exposed portions of theintermediate nanosheet stack structures in source/drain regions adjacentto the gate structures G1, G2, and G2 down to the substrate 100 and/orisolation layer. The etch process results in defining the overall lengthL (in the X-direction) of the individual nanosheet stack structures110-1˜110-6. The gate widths W_(G) (in the Y-direction) of the nanosheetstack structures 110-1˜110-6 are maintained since the sidewall surfacesof the nanosheet stack structures 110-1˜110-6 which define the gatewidth W_(G) are covered by the dummy gate layers 120 and 122, and thegate sidewall spacers 126.

A next stage of the fabrication process comprises forming the embeddedgate sidewall spacers 128 within sidewalls of the nanosheet stackstructures 110-1˜110-6 using known methods. For example, in oneexemplary process flow, the process begins by laterally recessing (inthe X-direction) exposed sidewall surfaces of the sacrificial nanosheetlayers 111, 113, 115, and 117 of the nanosheet stack structures110-1˜110-6 to form recesses in the sidewalls of the nanosheet stackstructures 110-1˜110-6. The depth of the lateral recess is controlledthrough a timed etch. In one embodiment, the exposed sidewall surfacesof the sacrificial nanosheet layers 111, 113, 115, and 117 are recessedto a depth which is equal to a lateral thickness of the gate sidewallspacers 126. The lateral etch process can be performed using anisotropic wet etch process with an etch solution that is suitable toetch the semiconductor material (e.g., SiGe) of the sacrificialnanosheet layers 111, 113, 115, and 117 of the nanosheet stackstructures 110-1˜110-6 selective to the semiconductor material (e.g.,Si) of the active nanosheet channel layers 112, 114, and 116, and otherexposed elements.

The embedded gate sidewall spacers 128 are then formed by depositing aconformal layer of dielectric material over the semiconductor IC deviceuntil the recesses in the sidewalls of the nanosheet stack structures110-1˜110-6 are filled with dielectric material, followed by an etchback to remove the excess dielectric material from the gate structureand the substrate 100. The dielectric material is deposited using ahighly conformal deposition process, such as ALD, to ensure that therecesses are sufficiently filled with dielectric material. The embeddedgate sidewall spacers 128 can be formed of the same dielectric materialused to form the gate sidewall spacer 126. For example, the embeddedgate sidewall spacers 128 can be formed of SiN, SiBCN, SiCO, SiBCN,SiCON, or any other suitable type of dielectric material (e.g., a low-kdielectric material having a k of less than 5, wherein k is the relativedielectric constant). The conformal layer of dielectric material can beetched back using an isotropic (wet or dry) etch process to remove theexcess dielectric material, while leaving the dielectric material in therecesses to form the embedded gate sidewall spacers 128. The wet etchprocess may include, but is not limited to, buffered hydrofluoric acid(BHF), diluted hydrofluoric acid (DHF), hydrofluoric nitric acid (HNA),phosphoric acid, HF diluted by ethylene glycol (HFEG), hydrochloric acid(HCl), or any combination thereof.

Following formation of the embedded gate sidewall spacers 128, theprocess flow continues with formation of the source/drain layers 130-137of the nanosheet FET device D1, D2, D3, and D4. The source/drain layers130-137 are formed by epitaxially growing semiconductor material (e.g.,epitaxial Si material, SiGe material, carbon-doped silicon (Si:C)material) on the exposed sidewall surfaces of the active nanosheetchannel layers 112, 114, and 116 using known techniques such as CVD,MOCVD, LPCVD, MBE, VPE, or other known epitaxial growth techniques whichare suitable for the given process flow. The exposed sidewall surfacesof the active nanosheet channel layers 112, 114, and 116 of thenanosheet stack structures 110-1˜110-6 provide surface areas to seed theepitaxial growth of the source/drain layers 130-137. The type ofepitaxial semiconductor material that is used to form the source/drainlayers 130-137 will vary depending on, e.g., the device type (e.g.,N-type or P-type) of the nanosheet FET devices, etc. The source/drainlayers N-type nanosheet FET devices and P-type nanosheet FET devices areformed using separate epitaxial deposition processes.

In some embodiments, as shown in FIGS. 1A and 1B, the epitaxial growthof the source/drain layers 130-137 on the ends of the active nanosheetchannel layers 112, 114 and 116 is performed so that the epitaxialmaterial merges (in the X and Z-directions) to form merged source/drainlayers 130-137 between the nanosheet stack structures 110-1˜110-6.Furthermore, in some embodiments, the source/drain layers 130-137 aredoped using known techniques. For example, in one embodiment, thesource/drain layers 130-137 are “in-situ” doped during epitaxial growthby adding a dopant gas to the source deposition gas (i.e., theSi-containing gas). Exemplary dopant gases may include a boron (B)containing gas such as BH₃ for P-type FETs or a phosphorus (P) orarsenic (As) containing gas such as PH₃ or AsH₃ for n-type FETs, whereinthe concentration of impurity in the gas phase determines itsconcentration in the epitaxially grown semiconductor material.

The use of an in-situ doping process is merely an example. For instance,an ex-situ process may be used to introduce dopants into thesource/drain layers. Other doping techniques can be used to incorporatedopants in the source/drain layers. Dopant techniques include but arenot limited to, ion implantation, gas phase doping, plasma doping,plasma immersion ion implantation, cluster doping, infusion doping,liquid phase doping, solid phase doping, in-situ epitaxy growth, or anysuitable combination of those techniques.

In addition, in some embodiments, a thermal anneal process is performedfollowing the epitaxial growth and doping of the source/drain layers130-137 to cause dopants to be injected into the end portions of theactive nanosheet channel layers 112, 114, and 116 that are in contactwith the epitaxial semiconductor material of the source/drain layers30-137. This anneal process effectively results in extending thesource/drain layers into the semiconductor material of the end portionsof the active nanosheet channel layers 112, 114, and 116, which resultsin a decrease in the parasitic resistance of the nanosheet FET devicesD1, D2, D3 and D4. In other embodiments, the thermal anneal process isperformed in later process (such as after the formation of the high-kgate dielectric layers) so that the same anneal process can serve twopurposes at the same time: driving dopants into the active nanosheetchannel layers, and improve the reliability of the high-k gatedielectric.

Following the formation of the epitaxial source/drain layers 130-137,the process flow continues with forming the insulating layer 140 (e.g.,ILD layer, or PMD layer) to encapsulate the gate structures G1, G2, G3and the source/drain layers 130-137 in dielectric/insulating material.In one embodiment, the insulating layer 140 is formed by depositing ablanket layer of dielectric/insulating material over the semiconductorIC device and planarizing the layer of dielectric/insulating materialdown to the gate capping layer 124 to form the insulating layer 140, asshown schematically shown in FIGS. 1A and 1B.

The insulating layer 140 may comprise any suitable insulating/dielectricmaterial that is commonly utilized in semiconductor process technologiesincluding, but not limited to, silicon oxide, silicon nitride, siliconoxynitride, SiCOH, SiCH, SiCNH, or other types of silicon-based low-kdielectrics (e.g., k less than about 4.0), porous dielectrics, known ULK(ultra-low-k) dielectric materials (with k less than about 2.5), or anysuitable combination of those materials. The dielectric/insulatingmaterial of the insulating layer 140 is deposited using known depositiontechniques, such as, for example, ALD, CVD, PECVD, PVD, or spin-ondeposition. In one embodiment, the layer of dielectric/insulatingmaterial is planarized using a standard planarization process such asCMP to remove the overburden dielectric/insulating down to the uppersurface of the dummy gate capping layers 124. In some embodiments, theinsulating layer 140 comprises a conformal silicon nitride liner that isinitially formed on the exposed surfaces of dummy gate structure andsource/drain layers 130-137 before blanket depositing one or moreinsulating materials to form the insulating layer 140.

A next phase of the fabrication process comprises forming a singlediffusion break isolation structure in the single diffusion break regionR3 to isolate the nanosheet FET devices of the first and second activeregions R1 and R2, using a process flow as schematically illustrated inFIGS. 2-5. In particular, FIG. 2 is a schematic cross-sectional sideview of the intermediate device structure shown in FIGS. 1A and 1B afterforming an etch mask 145 which comprises an opening 145-1 to expose thegate structure G3 in the single diffusion break region R3 and afterremoving the dummy gate layers of the gate structure G3 to expose thenanosheet stack structures 110-5 and 110-6 in the single diffusion breakregion R3. In one embodiment, the etch mask 145 comprises an organicplanarizing layer (OPL) or any other type of material which isself-leveling and achieves planarization over the surface topographywithout the use of etching, chemical mechanical polishing, or otherconventional planarization techniques. The etch mask 145 islithographically patterned using a lithographic stack comprising, e.g.,an antireflection coating (ARC) layer and a photoresist mask.

In some embodiments, the exposed dummy gate capping layer 124 of thegate structure G3 is removed by etching away the dielectric material(e.g., SiN) of the gate capping layer 124 selective to the materials ofthe gate sidewall spacer 126 (e.g., SiBCN) and the insulating layer 140(e.g., silicon oxide) to expose the underlying dummy gate electrodelayer 122. The dummy gate electrode layer 122 (e.g., sacrificialpolysilicon layer, or amorphous silicon layer) and dummy gate oxidelayer 120 are then etched away using known etching techniques and etchchemistries to form an open gate region 147. For example, thesacrificial dummy gate polysilicon material can be removed using aselective dry etch or wet etch process with suitable etch chemistries,including ammonium hydroxide (NH₄OH), tetramethylammonium hydroxide(TMAH), or SF6 plasma. After the polysilicon material is removed, anoxide etch process is performed to etch away the dummy gate oxide layer120.

Next, FIG. 3 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 2 after performing ananisotropic etch process to vertically etch the exposed nanosheet stackstructures 110-5 and 110-6 in the single diffusion break region R3 downto the surface of the underlying substrate 100 or isolation layer (notshown). In one embodiment, the anisotropic etch process is performedusing a RIE process with an etch chemistry that is configured to etchthe epitaxial semiconductor materials (e.g., Si and SiGe) that form thevarious nanosheet layers 111-117. As shown in FIG. 3, at the completionof the anisotropic etch process, the open gate region 147 extends downto the upper surface of the substrate 100 and end portions of thenanosheet channel layers 112, 114 and 116 remain disposed between theembedded sidewall spacers 128.

Next, FIG. 4 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 3 after removing the etchmask 145 and performing an oxidation process to oxidize the remainingend portions of the nanosheet channel layers 112, 114, and 116 andthereby form embedded oxide layers 150. The etch mask 145 is removedusing known methods (e.g., ashing). The oxidation process is performedusing any suitable isotropic oxidation process, such as plasmaoxidation, to oxidize the end portions of the nanosheet channel layers112, 114, 116 between the embedded sidewall spacers 128. In someembodiments, when the nanosheet channel layers 112, 114 and 116 compriseepitaxial Si material, the oxide layers 150 comprise silicon oxidelayers that are formed by oxidation of the epitaxial Si material. Theoxide layers 150 essentially comprise second embedded gate sidewallspacers that are disposed between the first gate sidewall spacers 128.

Next, FIG. 5 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 4 after filling the opengate region 147 with insulating material 160 to thereby completeformation of a single diffusion break isolation structure 165. In someembodiments, the insulating material 160 comprises the same or similarmaterial that forms the insulating layer 140. For example, in oneembodiment, the insulating material 160 comprises silicon oxide. Theopen gate region 147 is filled by depositing a layer of insulatingmaterial (e.g. silicon oxide) until the open gate region 147 is filled,and then performing a CMP process to remove the overburden insulatingmaterial and planarize the surface of the semiconductor IC device downto the gate capping layers 124 of the gate structures G1 an G2,resulting in the intermediate structure shown in FIG. 5. In theexemplary embodiment of FIG. 5, the single diffusion break isolationstructure 165, which is collectively comprised of the gate sidewallspacer 126, the embedded sidewall spacers 128, the oxide layers 150, andthe insulating layer 160, serves to isolate the nanosheet FET devices D1and D3 in the first active region R1 from the nanosheet FET devices D2and D4 in the second active region R2.

Following the formation of the single diffusion break isolationstructure 165, a replacement metal gate process is performed to replacethe sacrificial gate dummy gate materials of the gate structures G1 andG2 with a HKMG structure, using a process flow as schematicallyillustrated in FIGS. 6 and 7. For example, FIG. 6 is a schematiccross-sectional view of the intermediate device structure shown in FIG.5 after removing the dummy gate capping layer 124 and the dummy gatesacrificial layers (e.g., the dummy gate oxide layer 120 and the dummygate electrode layer 122) of the gate structures G1 and G2, and afterremoving the sacrificial nanosheet layers 111, 113, 115, and 117 torelease the active nanosheet channel layers 112, 114 and 116 of thenanosheet stack structures 110-1, 110-2, 110-3, and 110-4 and form opengate regions 149. The gate capping layers 124 and dummy gate layers 122and 120 are removed using techniques as discussed above. The dummy oxidelayers 120 are removed using an oxide etch process that is highlyselective to, e.g., the active nanosheet channel layers 112, 114, and116. In this manner, the sacrificial materials (e.g., dummy polysiliconand oxide layers) of the dummy gate can be etched away without damagingthe active nanosheet channel layers 112, 114, and 116 of the nanosheetstack structures 110-1, 110-2, 110-3, and 110-4.

After removing the dummy gate layers 122 and 120, an etch process isperformed to selectively etch away the sacrificial nanosheet layers 111,113, 115, and 117 of the nanosheet stack structures 110-1, 110-2, 110-3,and 110-4 and thereby release the active nanosheet channel layers 112,114, and 116 and extend the open gate regions 149 into spaces betweenand adjacent to the active nanosheet channel layers 112, 114, and 116.The sacrificial nanosheet layers 111, 113, 115, and 117 (e.g., SiGelayers) are etched selective to the active nanosheet channel layers 112,114, and 116 (e.g., Si layers). In one embodiment, the SiGe material ofthe sacrificial nanosheet layers 111, 113, 115, and 117 can beselectively etched (with high etch selectivity) using a gas phase HCl(hydrochloric acid) or wet etch solution containing hydrogen peroxide(H₂O₂) to etch the SiGe material of the sacrificial nanosheet layers111, 113, 115, and 117 selective to the Si material of the activenanosheet channel layers 112, 114, and 116. The gas phase HCl(hydrochloric acid) provides high etch selectivity when, for example,the active nanosheet channel layers 112, 114, and 116 are formed of Sior SiGe with a lower Ge concentration than the SiGe material of thesacrificial nanosheet layers 111, 113, 115, and 117.

Next, FIG. 7 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 6 after forming HKMGstructures 170-1 and 170-2 for the gate structures G1 and G2,respectively. The HKMG structure 170-1 comprises a common metal gatestructure for the nanosheet FET devices D1 and D3 in the first activeregion R1, and the HKMG structure 170-2 comprises a common metal gatestructure for the nanosheet FET devices D2 and D4 in the second activeregion R2. The HKMG structures 170-1 and 170-2 each comprise high-k gatedielectric layers 172 that are formed on exposed surfaces of the activenanosheet channel layers 112, 114 and 116, and a metal gate layer 174formed over the high-k gate dielectric layers 172.

In one embodiment, the HKMG structures 170-1 and 170-2 are formed bydepositing one or more conformal layers of high-k gate dielectricmaterial over the exposed surfaces of the semiconductor structure toconformally cover the surfaces of the active nanosheet channel layers112, 114, and 116. The high-k gate dielectric layers 172 are preferablyformed of high-k dielectric material having a dielectric constant ofabout 3.9 or greater. For example, the gate dielectric material caninclude but is not limited to metal oxides such as hafnium oxide,hafnium silicon oxide, hafnium silicon oxynitride, hafnium zirconiumoxide, and nitride films thereof. In other embodiments, the high-kdielectric may comprise lanthanum oxide, lanthanum aluminum oxide,zirconium oxide, zirconium silicon oxide, zirconium silicon oxynitride,tantalum oxide, titanium oxide, barium strontium titanium oxide, bariumtitanium oxide, strontium titanium oxide, yttrium oxide, aluminum oxide,lead scandium tantalum oxide, and lead zinc niobate. The high-kdielectric material may further include dopants such as lanthanum,aluminum. In one embodiment of the invention, the conformal high-k gatedielectric layers 172 are formed with a thickness in a range of about0.5 nm to about 2.0 nm, which will vary depending on the targetapplication. The conformal layer of high-k gate dielectric material isdeposited using known methods such as ALD, for example, which allows forhigh conformality of the gate dielectric material.

As is known in the art, the use of high-k gate dielectric materials canbe problematic in that such dielectric materials typically do notinterface well with silicon layers. For example, high-k gate dielectricmaterials do not passivate a silicon surface, which results in a largenumber of interface traps and charges and other issues which can degradedevice performance. As such, in one exemplary embodiment, beforedepositing the high-k dielectric material to form the high-k gatedielectric layers 172, a channel pre-clean process is performed to cleanthe exposed silicon surfaces of the active nanosheet channel layers 112,114, and 116, which is then followed by an oxidation process to formultra-thin interfacial silicon oxide layers on the exposed surfaces ofthe active nanosheet channel layers 112, 114, and 116. In one exemplaryembodiment, the interfacial silicon oxide layers are formed using achemical oxidation process with an ozonated deionized water comprisingozone, and a suitable oxidation temperature, ozone concentration in thedeionized water, and chemical oxidation process time to form thininterfacial silicon oxide layers. The interfacial layers are formed byoxidizing the exposed silicon surfaces of the active nanosheet channellayers 112, 114, and 116 to form thin interfacial silicon oxide layerswith a thickness in a range of about 5 angstroms to about 10 angstroms(i.e., about 0.5 nm to about 1 nm). It is to be understood that theformation of the interfacial silicon oxide layers is an optional stepand that in other embodiments of the invention, the high-k dielectricmaterial of the HKMG structures 170-1 and 170-2 can be formed on theexposed silicon surfaces of the active nanosheet channel layers 112,114, and 116 without initially forming the thin interfacial oxidelayers.

In some embodiments, the metal gate layers 174 comprises one or morework function metal layers which are conformally deposited over thehigh-k gate dielectric layer 172. The work function metal layer(s) maycomprise one or more types of metallic materials, including, but notlimited to, titanium nitride (TiN), tantalum nitride (TaN), and anAl-containing alloy (e.g., TiAlC, TiAl, and AlC, or nitrided alloysthereof). In other embodiments, the work function metal layer(s) maycomprise a metallic material which comprises a composition or alloy ofZr, W, Hf, Ti, Al, Ru, Pa, ZrAl, WAl, TaAl, HfAl, TaC, TiC, TaMgC, andother types, compositions, or alloys of work function metals that arecommonly used to obtain target work functions for the nanosheet FETdevices. The work function metal layers are conformally deposited usingknown methods such as ALD, CVD, etc., which allow for high conformalityof the deposited work function metal layers.

In some embodiments, the work function metal layers completely fill thespaces above and below the active nanosheet channel layers 112, 114, and116. Indeed, in instances where the initial spacing between the activenanosheet channels 112, 114 and 116 is relatively small (e.g., 7 nm to10 nm), after formation of the high-k dielectric layer 172, theconformal deposition of a stack of two or more work function metallayers can result in filling (i.e., pinch-off) the spaces above andbelow the active nanosheet channel layers 112, 114, and 116 such thatthe spaces are filled with gate dielectric material and work functionmetal. This is sufficient for short-channel length nanosheet FET deviceswhere L_(G) is about 15 nm or less.

Furthermore, in some embodiments, the remaining portions of the opengate regions 149 above the active nanosheet channel layers 116 can befilled with work function metal by continuing the deposition process forthe last deposited work function metal layer until the open gate regions149 above the active nanosheet channel layers 116 are completely filledwith the work function metal layer. In other embodiments, the remainingportion of the open gate regions 149 can be filled with a low-resistancemetallic material such as tungsten, ruthenium, cobalt, copper, aluminum,etc., to form a metallic gate electrode apart from the work functionmetal.

Following the deposition of the dielectric and metallic materials thatform the HKMG structures 170-1 and 170-2, a CMP process is performed topolish the surface of the semiconductor device structure down to the ILDlayer 140, thereby removing overburden portions of the gate dielectric,work function, and gate electrode layers, resulting in the semiconductorstructure shown in FIG. 7. Following formation of the HKMG structures170-1 and 170-2, any known sequence of processing steps can be performedto complete the fabrication of the semiconductor integrated circuitdevice, the details of which are not needed to understand embodiments ofthe invention.

Briefly, following the formation of the HKMG structures 170-1 and 170-2,an etch process can be performed to recess an upper surface of the HKMGstructures 170-1 and 170-2 down to a target level below the uppersurface of the insulating layer 140. A layer of dielectric material isthen deposited over the surface of the semiconductor device structure tofill the area above the recessed surfaces of the HKMG structures 170-1and 170-2 with dielectric material, and the semiconductor devicestructure is planarized down to the surface of the insulating layer 140to remove the overburden dielectric material, and thereby form gatecapping layers. The gate capping layers can be formed of a dielectricmaterial such as SiN or SiBCN, etc. Next, middle-of-the-line (MOL)processing can continue to form MOL contacts such as verticalsource/drain contacts and gate contacts, etc., using known materials andfabrication techniques. Then, a back-end-of-line (BEOL) process modulecan be performed to fabricate a BEOL interconnect structure whichprovides connections to/between the MOL contacts, and other active orpassive devices that are formed as part of the front-end-of-line (FEOL)layer.

FIGS. 8 through 10 schematically illustrate a method for fabricating asemiconductor IC device 20 having single diffusion break isolationstructures for isolating nanosheet FET devices, according to anotherexemplary embodiment of the invention. In particular, FIGS. 8-10schematically illustrate a process for fabricating an alternativeembodiment of a single diffusion break isolation structure in the singlediffusion break region R3 to isolate the nanosheet FET devices of thefirst and second active regions R1 and R2. The method of FIGS. 8-10begins with the process flow and intermediate structures as discussedabove in conjunction with FIGS. 1A, 1B, 2 and 3, the details of whichwill not be repeated. FIG. 8 is a schematic cross-sectional side view ofthe intermediate device structure shown in FIG. 3 after removing theetch mask 145 and after removing the remaining end portions of thenanosheet channel layers 112, 114, and 116 to thereby form recessregions 200 between the embedded sidewall spacers 128. The etch mask 145is removed using known methods (e.g., ashing). The end portions of thenanosheet channel layers 112, 114, 116 disposed between the embeddedsidewall spacers 128 are removed using any suitable horizontal conformalrecess etch process. The recess process is performed using a timed etchto prevent gouging of the source/drain layers 131 and 132 and othersource/drain layers disposed adjacent to the single diffusion breakregion R3.

Next, FIG. 9 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 8 after filling the recessregions 200 with dielectric material to form second embedded sidewallspacers 210 between the first embedded sidewall spacers 128. The secondembedded sidewall spacers 210 are formed by depositing a conformal layerof dielectric material until the recess regions 200 are filled withdielectric material (e.g., until pinch-off of the dielectric materialoccurs in the recess regions 200), followed by an etch back to removethe excess dielectric material from the sidewall and bottom surfaces ofthe open gate region 147. The dielectric material is deposited using ahighly conformal deposition process, such as ALD, to ensure that therecess regions 200 are sufficiently filled with dielectric material. Thesecond embedded sidewall spacers 210 can be formed of the same orsimilar dielectric material used to form the first embedded sidewallspacers 128 and/or the gate sidewall spacers 126. The conformal layer ofdielectric material that is deposited to fill the recess regions 200 canbe etched back using an isotropic (wet or dry) etch processes to removethe excess dielectric material, while leaving the dielectric material inthe recess regions 200 to form the second embedded sidewall spacers 210and avoiding over etching or gouging of the first embedded sidewallspacers 128. The wet etch process may include, but is not limited to,buffered hydrofluoric acid, diluted hydrofluoric acid, hydrofluoricnitric acid, phosphoric acid, HF diluted by ethylene glycol,hydrochloric acid, or any combination thereof.

Next, FIG. 10 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 9 after filling the opengate region 147 with insulating material 260 to thereby completeformation of a single diffusion break isolation structure 265. In someembodiments, the insulating material 260 comprises the same or similarmaterial that forms the insulating layer 140. For example, in oneembodiment, the insulating material 260 comprises silicon oxide. Theopen gate region 147 is filled by depositing a layer of insulatingmaterial (e.g. silicon oxide) until the open gate region 147 is filled,and then performing a CMP process to remove the overburden insulatingmaterial and planarize the surface of the semiconductor IC device downto the gate capping layers 124 of the gate structures G1 an G2,resulting in the intermediate structure shown in FIG. 10.

In the exemplary embodiment of FIG. 10, the single diffusion breakisolation structure 265, which is collectively comprised of the gatesidewall spacer 126, the embedded sidewall spacers 128 and 210, and theinsulating layer 260, serves to isolate the nanosheet FET devices D1 andD3 in the first active region R1 from the nanosheet FET devices D2 andD4 in the second active region R2. Following formation of the singlediffusion break isolation structure 265, the fabrication processcontinues by performing a replacement metal gate process as discussedabove in conjunction with FIGS. 6 and 7 to form HKMG structures of thegate structures G1 and G2.

FIGS. 11 and 12 schematically illustrate a method for fabricating asemiconductor IC device 30 having single diffusion break isolationstructures for isolating nanosheet FET devices, according to anotherexemplary embodiment of the invention. In particular, FIGS. 11 and 12schematically illustrate a process for fabricating an alternativeembodiment of a single diffusion break isolation structure in the singlediffusion break region R3 to isolate the nanosheet FET devices of thefirst and second active regions R1 and R2. The method of FIGS. 11 and 12begins with the process flow and intermediate structures as discussedabove in conjunction with FIGS. 1A, 1B, and 2, the details of which willnot be repeated. FIG. 11 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 2 after removing the etchmask 145 and after selectively etching away the sacrificial nanosheetlayers 111, 113, 115, and 117 of the exposed nanosheet stack structures110-5 and 110-6 in the single diffusion break region R3. The sacrificialnanosheet layers 111, 113, 115, and 117 are etched selective to thenanosheet channel layers 112, 114, and 116 (and other surroundingmaterials and structures) using the same or similar techniques asdiscussed above.

Next, FIG. 12 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 11 after oxidizing thenanosheet channel layers 112, 114, and 116 to form oxide layers 312,314, and 316, and after filling the open gate region 147 with insulatingmaterial 360 to thereby complete formation of a single diffusion breakisolation structure 365. The nanosheet channel layers 112, 114 and 116are oxidized using known techniques which allow the epitaxial siliconmaterial of the nanosheet channel layers 112, 114 and 116 to beconverted to silicon oxide material. For example, the oxidation processcan be performed using a plasma oxidation process or a chemicaloxidation process using ozonated deionized water, etc. In someembodiments, the insulating material 360 comprises the same or similarmaterial that forms the insulating layer 140. For example, in oneembodiment, the insulating material 360 comprises silicon oxide. Theopen gate region 147 is filled by depositing a layer of insulatingmaterial (e.g. silicon oxide) until the open gate region 147 is filled,and then performing a CMP process to remove the overburden insulatingmaterial and planarize the surface of the semiconductor IC device downto the gate capping layers 124 of the gate structures G1 an G2,resulting in the intermediate structure shown in FIG. 12.

In the exemplary embodiment of FIG. 12, the single diffusion breakisolation structure 365, which is collectively comprised of the gatesidewall spacer 126, the embedded sidewall spacers 128, the oxide layers312, 314 and 316, and the insulating layer 360, serves to isolate thenanosheet FET devices D1 and D3 in the first active region R1 from thenanosheet FET devices D2 and D4 in the second active region R2.Following formation of the single diffusion break isolation structure365, the fabrication process continues by performing a replacement metalgate process as discussed above in conjunction with FIGS. 6 and 7 toform HKMG structures of the gate structures G1 and G2.

FIGS. 13A through 16 schematically illustrate a method for fabricating asemiconductor IC device having single diffusion break isolationstructures for isolating nanowire FET devices, according to an exemplaryembodiment of the invention. To begin, FIGS. 13A and 13B schematicallyillustrate a semiconductor IC device 40 at an initial stage offabrication comprising a plurality of nanowire FET devices D1, D2, D3,and D4 formed on a semiconductor substrate 100. FIG. 13A is a schematictop plan view (X-Y plane) of the semiconductor IC device 40 and FIG. 13Bis a schematic cross-sectional side view (X-Z plane) of thesemiconductor IC device 40 along line 13B-13B in FIG. 13A. Thesemiconductor IC device 40 as shown in FIGS. 13A and 13B is similar inconfiguration to the semiconductor IC device 10 of FIGS. 1A and 1B,except that that nanowire FET devices D1, D2, D3 and D4 comprisenanowire stack structures with gate widths W_(G) that are the same orsmaller than the thickness of the spacers 126 (e.g., nanowire channellayers have a critical dimension (CD) that is similar or smaller thanthe CD of the spacers 126).

More specifically, nanowire device D1 comprises a nanowire stackstructure 410-1 and source/drain layers 130 and 131. The nanowire deviceD2 comprises a nanowire stack structure 410-2 and source/drain layers132 and 133. The nanowire device D3 comprises a nanowire stack structure410-3 and source/drain layers 134 and 135. The nanowire device D4comprises a nanowire stack structure 410-4 and source/drain layers 136and 137. The single diffusion break region R3 comprises a nanowire stackstructure 410-5 disposed between the source/drain layers 131 and 132,and a nanowire stack structure 410-6 disposed between the source/drainlayers 135 and 136. The nanowire stack structures 410-1˜410-6 eachcomprise a plurality of epitaxial semiconductor layers 411, 412, 413,414, 415, 416, and 417, which include sacrificial nanowire layers 411,413, 415, and 417, and active nanowire channel layers 412, 414, and 416,wherein the active nanowire channel layer 412, 414, and 416 is disposedbetween sacrificial layers 411, 413, 415, and 417. The intermediatestructure of the semiconductor IC device 40 shown in FIGS. 13A and 13Bis formed using known fabrication methods including, for example, thefabrication methods as discussed above for fabricating the semiconductorIC device 10 of FIGS. 1A and 1B, the details of which will not berepeated.

FIG. 14 is a schematic cross-sectional side view of the intermediatedevice structure shown in FIGS. 13A and 13B after removing the dummygate layers of the gate structure G3 to form an open gate region 147which exposes the nanowire stack structures 410-5 and 410-6 in thesingle diffusion break region R3, and after selectively etching away thenanowire channel layers 412, 414, and 416 of the exposed nanowire stackstructures 410-5 and 410-6 in the single diffusion break region R3 toform spaces 420 between the sacrificial nanowire layers 411, 413, 415,and 417. The dummy gate capping layer 124 and dummy gate layers 120 and122 of the gate structure G3 are removed using etching methods asdiscussed above. The nanowire channel layers 412, 414, and 416 (e.g.,epitaxial Si layers) are etched selective to the sacrificial nanowirelayers 411, 413, 415, and 417 (e.g., epitaxial SiGe layers) and othersurrounding materials and structures using the same or similartechniques as discussed above. In this embodiment, the small width W_(G)(or diameter) of the nanowire channel layers 412, 414, and 416 allowsthe nanowire channel layers 412, 414, and 416 to be isotropically etchedand form the spaces 420 without gouging the areas of the source/drainlayers (e.g., source drain layer 131 and 132, as shown in FIG. 14) thatare in contact with the end portions of the nanowire channel layers 412,414, and 416.

Next, FIG. 15 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 14 after forming dielectriclayers 422 in the spaces 420 between the sacrificial nanowire layers411, 413, 415, and 417. In some embodiments, the dielectric layers 422are formed by depositing a conformal layer of dielectric material untilthe spaces 420 are filled with dielectric material (e.g., untilpinch-off of the dielectric material occurs in the spaces 420), followedby a conformal etch back to remove the excess/overburden dielectricmaterial from the sidewall and bottom surfaces of the open gate region147 and the upper surface of the ILD layer 140. The dielectric materialis deposited using a highly conformal deposition process, such as ALD,to ensure that the spaces 420 are sufficiently filled with dielectricmaterial to form the dielectric layers 422. The dielectric layers 422can be formed of the same or similar dielectric material used to formthe embedded sidewall spacers 128 and/or the gate sidewall spacers 126.The overburden material of the conformal layer of dielectric materialthat is deposited to fill the spaces 420 and form the dielectric layers422 can be conformally etched back using an isotropic (wet or dry) etchprocesses to remove the excess dielectric material.

Next, FIG. 16 is a schematic cross-sectional side view of theintermediate device structure shown in FIG. 15 after filling the opengate region 147 with insulating material 460 to thereby completeformation of a single diffusion break isolation structure 465. In someembodiments, the insulating material 460 comprises the same or similarmaterial that forms the insulating layer 140. For example, in oneembodiment, the insulating material 460 comprises silicon oxide. Theopen gate region 147 is filled by depositing a layer of insulatingmaterial (e.g. silicon oxide) until the open gate region 147 is filled,and then performing a CMP process to remove the overburden insulatingmaterial and planarize the surface of the semiconductor IC device downto the gate capping layers 124 of the gate structures G1 an G2,resulting in the intermediate structure shown in FIG. 16.

In the exemplary embodiment of FIG. 16, the single diffusion breakisolation structure 665, which is collectively comprised of the gatesidewall spacer 126, the embedded sidewall spacers 128, the sacrificialnanowire layers 411, 413, 415, and 417 and the dielectric layers 422,serves to isolate the nanosheet FET devices D1 and D3 in the firstactive region R1 from the nanosheet FET devices D2 and D4 in the secondactive region R2. Following formation of the single diffusion breakisolation structure 465, the fabrication process continues by performinga replacement metal gate process as discussed above in conjunction withFIGS. 6 and 7 to form HKMG structures of the gate structures G1 and G2.

It is to be understood that the exemplary methods discussed herein forfabricating for fabricating semiconductor integrated circuit devicehaving single diffusion break isolation structures for isolatinggate-all-around FET devices (such as nanosheet FET devices, nanowiredevices, etc.) can be readily incorporated within semiconductorprocessing flows, semiconductor devices, and integrated circuits withvarious analog and digital circuitry or mixed-signal circuitry. Inparticular, integrated circuit dies can be fabricated with variousdevices such as field-effect transistors, bipolar transistors,metal-oxide-semiconductor transistors, diodes, capacitors, inductors,etc. An integrated circuit in accordance with the present invention canbe employed in applications, hardware, and/or electronic systems.Suitable hardware and systems for implementing the invention mayinclude, but are not limited to, personal computers, communicationnetworks, electronic commerce systems, portable communications devices(e.g., cell phones), solid-state media storage devices, functionalcircuitry, etc. Systems and hardware incorporating such integratedcircuits are considered part of the embodiments described herein. Giventhe teachings of the invention provided herein, one of ordinary skill inthe art will be able to contemplate other implementations andapplications of the techniques of the invention.

Although exemplary embodiments have been described herein with referenceto the accompanying figures, it is to be understood that the inventionis not limited to those precise embodiments, and that various otherchanges and modifications may be made therein by one skilled in the artwithout departing from the scope of the appended claims.

What is claimed is:
 1. A semiconductor integrated circuit device,comprising: a first gate-all-around field-effect transistor devicedisposed in a first device region of a semiconductor substrate; a secondgate-all-around field-effect transistor device disposed in a seconddevice region of the semiconductor substrate; and a single diffusionbreak isolation structure disposed between the first and second deviceregions; wherein the single diffusion break isolation structurecomprises a dummy gate structure disposed on the semiconductor substratebetween a first source/drain layer of the first gate-all-aroundfield-effect transistor device and a second source/drain layer of thesecond gate all-around field-effect transistor device, wherein thesingle diffusion break isolation structure is configured to electricallyisolate the first and second source/drain layers; wherein the singlediffusion break isolation structure comprises: a gate sidewall spacerthat surrounds and defines a dummy gate region; and a layer ofinsulating material disposed in the dummy gate region; wherein the gatesidewall spacer comprises first embedded sidewall spacers that are incontact with the first and second source/drain layers, wherein the firstembedded sidewall spacers comprise a dielectric material comprisingsilicon and nitrogen, and second embedded sidewall spacers that are incontact with the first and second source/drain layers, wherein thesecond embedded sidewall spacers comprise oxidized epitaxial siliconmaterial, wherein the second embedded sidewall spacers are disposedbetween the first embedded sidewall spacers and do not extend into thedummy gate region.
 2. The device of claim 1, wherein the second embeddedsidewall spacers comprise oxidized end portions of epitaxial siliconchannel layers which remain after removing portions of the epitaxialsilicon channel layers from within the dummy gate region such that thedummy gate region is devoid of portions of the epitaxial silicon channellayers.
 3. The device of claim 1, wherein the layer of insulatingmaterial disposed in the dummy gate region comprises silicon oxide. 4.The device of claim 1, wherein the first and second gate-all-aroundfield-effect transistor devices comprise nanosheet field-effecttransistor devices.
 5. The device of claim 1, wherein the first andsecond gate-all-around field-effect transistor devices comprise nanowirefield-effect transistor devices.
 6. The device of claim 1, wherein thelayer of insulating material completely fills the dummy gate region. 7.The device of claim 1, wherein the layer of insulating material and thefirst embedded sidewall spacers comprise different materials.
 8. Thedevice of claim 7, wherein the layer of insulating material comprisessilicon oxide and wherein the first embedded sidewall spacers comprisesilicon nitride.
 9. The device of claim 1, wherein the layer ofinsulating material and the first embedded sidewall spacers comprise asame material.
 10. The device of claim 1, wherein the layer ofinsulating material and the first embedded sidewall spacers comprisesilicon nitride.
 11. The device of claim 1, wherein the first embeddedsidewall spacers comprise one of SiN, SiBCN, SiBCN, and SiCON.
 12. Thedevice of claim 1, wherein the layer of insulating material comprisesone of silicon nitride, silicon oxynitride, SiCOH, SiCH, and SiCNH.